is a rapidly acting fixative for animal tissues, containing mercuric chloride (" corrosive sublimate"), potassium dichromate
, sodium sulfate
Sodium sulfate is the sodium salt of sulfuric acid. When anhydrous, it is a white crystalline solid of formula Na2SO4 known as the mineral thenardite; the decahydrate Na2SO4·10H2O has been known as Glauber's salt or, historically, sal mirabilis since the 17th century. Another solid is the...
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
, and acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
. Zenker is usually made as follows.
- Mercuric chloride 50g
- Potassium dichromate 25g
- Sodium sulphate (decahydrate) 10g
- Distilled water to make 1000 ml
Before use add 5ml glacial acetic acid to 100ml of the stock solution. Both the stock solution and the complete Zenker fixative are stable for many years.
If the glacial acetic acid is been replaced by 5 ml of formalin (37-40% formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
)), the resulting solution is Helly's fixative, also sometimes called "formol-Zenker". Helly is stable for only a few hours because the formaldehyde and dichromate components react with one another, forming formic acid and chromic ions; the orange solution becomes greenish.
This fixative is named after Friedrich Albert von Zenker
Friedrich Albert von Zenker was a German pathologist and physician, celebrated for his discovery of trichinosis. He was born in Dresden, and was educated in Leipzig and Heidelberg. Attached to the city hospital of Dresden in 1851, he added, in 1855, the duties of professor of pathological...
(1825-1898), a German physician and pathologist.
Zenker's fixative is employed to prepare specimens of animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....
tissues for microscopial study. It provides excellent fixation of nuclear chromatin, connective tissue fibres and some cytoplasmic features but does not preserve delicate cytoplasmic organelles such as mitochondria. Helly's fixative is preferable for traditional staining of mitochondria with dyes.
Fixatives containing mercuric chloride or potassium dichromate are currently out of fashion because of the toxicity of these two compounds and the associated expense of disposing of hazardous waste. Mercuric chloride can be replaced with the same weight of less toxic zinc chloride but the resulting "zinc-Zenker" may not give the same quality of fixation as the original mixture.
Zenker's fluid or solution
— a fixative
A fixative is a stabilizing or preservative agent:*Fixative , a liquid usually sprayed over a finished piece of artwork to better preserve it and prevent smudging...
solution of corrosive mercuric chloride 5, potassium bichromate 2.5, sodium sulfate 1, water 100.